The Texas caucuses -- which offer up about a third of the state's delegates -- are still too close to call.

Obama didn't lose his lead, but he lost his momentum. The Illinois senator was on a 12-contest winning streak since Super Tuesday before Clinton stopped him by winning the two big prizes Tuesday night.

But because the Democratic delegates are allocated proportionally, the race appears to be headed to the party's convention in August. Clinton or Obama would need substantial wins in almost all of the remaining contests to get the magic number.

The Democrats' next big primary is seven weeks away. The race shifts to Pennsylvania, where 158 delegates are at stake. Wyoming and Mississippi hold contests before then, but there aren't as many delegates up for grabs.

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"Pennsylvania on paper is a good state for Clinton. It's a lot like Ohio demographically. Like in Ohio, she has the support of the very politically active governor, Ed Rendell. So I think Obama has his work cut out for him there," said Mark Halperin, a political analyst with Time magazine.

"There are not enough votes left among pledged delegates for anybody to win the nomination," said Mary Frances Berry, former chairwoman of the U.S. Civil Rights Commission. "One person's going to be ahead, one's going to be behind. It will come down to the superdelegates."

The nearly 800 superdelegates -- various party leaders and officials who cast their vote at the convention -- are free to vote for the candidate of their choice.

Based on superdelegates who have publicized their preference, Clinton leads Obama 238-199.

House Speaker Nancy Pelosi said Wednesday now is not the time for superdelegates to wade into the fight.

"I think the electoral process has to work its way," the California Democrat told reporters.

"There are still many voters unheard from yet, and I think that our candidates both have the capacity to inspire, to bring out a big vote that will hold us in good stead in November, and I think that now is not the time for anybody to weigh in."

Pelosi said she was confident the nominee would be decided before the Democratic convention in August, and that she was "never among those who believed this would be resolved by now."

She argued that the prolonged campaign is good for the party, and offers Democrats a chance to "make a clear distinction" about their differences with Republicans on a range of issues.

Tuesday's contests made Sen. John McCain the likely Republican nominee, so the Democrats are competing not only against each other but also against McCain.

While Democratic contenders fight for their party's bid, McCain can turn his attention to the general election.

Obama on Wednesday challenged Clinton's claim she was the best candidate to take on McCain in the fall.

"I think that I am in a much stronger position to run against the Republicans than she is, otherwise I wouldn't be running for president," he said.

Clinton said she could go "toe-to-toe" on national security issues with McCain.

"People who voted a month ago didn't know who the Republican nominee was going to be. They didn't perhaps factor in that it will be about national security because, indeed, with Sen. McCain, that's what it will be about," Clinton said Wednesday.

Clinton and Obama both say they will be their party's nominee, and while that's not possible, it is possible they could both appear on the Democratic ticket.

Clinton Wednesday said she would consider being part of what some Democrats call a "dream ticket" that would include both candidates.

"That may be where this is headed," the New York senator said on the "CBS Early Show." "But of course we have to decide who is on the top of ticket. I think the people of Ohio very clearly said that it should be me."

The Obama camp has avoided making similar statements.

Meanwhile, another big question looms over the election -- what do the Democrats do with Michigan and Florida? Clinton won both states, but no delegates were at stake because the states were penalized for violating party rules by scheduling their primaries early.

The Democratic candidates had agreed not to campaign in either state, and Clinton was the only major candidate on Michigan's ballot.

Clinton wants both states to count, and there's talk in Florida of a primary do-over. The problem is another primary would not come cheap.

"If the [Democratic National Committee] wants to talk about another Florida presidential primary, but not paid for by the taxpayers of Florida -- they have already paid $18 million for the presidential primary that was held. If the DNC were to pay for another election, then that might be considered," said Florida Sen. Bill Nelson, a Democrat.E-mail to a friend